When can Southern Steer enforce the provisions of the lease assignment?

Upon a default by Assignor under the Lease or under that certain franchise agreement ("Franchise Agreement") for a Southern Steer Business between Assignee and Assignor, or in the event of a default by Assignor under any document or instrument securing the Franchise Agreement, Assignee will have the right and is hereby empowered to take possession of the Premises demised by the Lease, expel Assignor therefrom, and, in that event, Assignor will have no further right, title or interest in the Lease.

Assignor agrees it will not suffer or permit any surrender, termination, amendment or modification of the Lease without the prior written consent of Assignee. Through the Initial Term of the Franchise Agreement and any Successor Terms thereof, Assignor agrees that it will elect and exercise all options to extend the term of or renew the Lease not less than thirty (30) days before the last day that said option must be exercised, unless Assignee otherwise agrees or instructs in writing. Upon failure of Assignee to otherwise agree in writing, and upon failure of Assignor to so elect to extend or renew the Lease as stated herein, Assignor hereby irrevocably appoints Assignee as its true and lawful attorney-in-fact, which appointment is coupled with an interest, to exercise the extension or renewal options in the name, place and stead of Assignor for the sole purpose of effecting the extension or renewal.

Source: Item 22 — ITEM. 22 CONTRACTS (FDD pages 61–168)